Pottery kilns require high temperatures to fire the pottery, with the temperature varying with the type of clay used, any glaze finish applied to the clay and other factors. In order to conserve fuel needed to maintain the high temperatures for firing, most kilns used insulated overs. But for larger pieces of pottery such closed kilns are too small. Further, some types of pottery firing, such as raku, use combustion products and smoke to achieve the desired finish, but the combustion products may coat the oven walls and adversely affect the firing of later pieces of pottery so closed, oven type kilns present problems for large pieces of raku pottery.
For large raku pottery, Laguna Clay makes a firing kiln that has firing chamber that is lifted vertically upward and downward on three vertical posts that are spaced apart around the firing chamber. The standard firing chamber is about 26-32 inches high, requiring the vertical frames to be more than twice that height in order for the chamber to clear the top of the longest pottery that may be placed in the firing chamber. That in turn requires a very tall space within which to place the kiln and limits the height of the firing chamber. Further, the three vertical frames impede access to the kiln both during firing and during loading and unloading of pottery into the kiln. Moreover, when the chamber is lifted it is very hot and having it suspended above the fired pottery makes it hazardous for users to access the fired pottery without touching the hot chamber. Even when the chamber is cool users must take care to avoid bumping their head on it. There is thus a need for an improved kiln that allows the firing of large pieces of pottery but does not require the high clearance of conventional kilns, and that provides better access to the inside of the kiln.
The Laguna kiln has three gas burners which are placed around the perimeter of the kiln floor, with the floor directing the flame from the burners directly up the wall of the firing chamber where they heat the pottery pieces by convection. That provides an updraft heater, but wastes a lot of heat as not only does heated gas rise, but the burners are effectively orientated so as to blow the hot gas outward and upward, where it vents through openings at the top of the kiln. There is thus a need for a more efficient heater for this type of kiln.